The discovery of high temperature superconductive materials in the late 1980's was soon followed by a desire to form such materials into wires, tapes or similar shapes. Ideally, such wires or tapes should be physically strong, flexible, highly conductive and able to withstand strong magnetic fields without loss of current carrying capacity.
Processes generally referred to as "powder in a tube" have been developed. One example is U.S. Pat. No. 4,983,576, by Hagino et al., which describes a general process of fabricating superconductive wire by initially preparing a superconductive powder, filling a tube or pipe of silver with the superconductive powder, sealing the pipe or tube, subjecting the pipe or tube to drawing operations to form wire, and finally sintering the drawn wire.
Unfortunately, the resultant wires and tapes do not always have all the desired properties such as, e.g., high current capacity together with good mechanical properties such as crack resistance. It can also be desirable in some applications to have a channel or cavity within the wire or tape thereby allowing for the passage of a cryogenic coolant.
Accordingly, it is an object of this invention to provide a superconductive article in the form of a wire or tape, said superconductive article having an inner cavity for passage of coolant.
Another object of the invention is to have a tubular-type geometry thereby providing a more rigid superconductive article.
Still another object of the invention is to have a superconductive material in a tubular-type geometry whereby such geometry reduces field dependence of the superconductive material.
It is a further object of this invention to provide a method of fabricating such a superconductive article having a tubular-type geometry.